Alternating dietary fat sources for growing-finishing pigs fed dried distillers grains with solubles: I. Growth performance, pork carcass characteristics, and fatty acid composition of subcutaneous fat depots.J Anim Sci. 2013 Mar; 91(3):1493-508.JA
Crossbred pigs (n = 216) were used to test the effects of phase-feeding beef tallow (BT) and yellow grease (YGr) on live performance, carcass characteristics, and fatty acid composition of subcutaneous (s.c.) fat depots of growing-finishing swine. Pigs were blocked by initial BW (26.0 ± 5.3 kg) before allotment to pens (6 pigs/pen), and pens (6 pens/block) were assigned randomly to 1 of 6 dietary treatments: 1) corn-soybean meal-based grower and finisher diets formulated with 4.7% YGr fed during all 5 feeding phases (YG15), 2) corn-soybean meal-based diets formulated with 5.0% BT fed during all 5 phases (BT15), 3) diets containing 5.0% BT fed during the first 2 phases and diets with 4.7% YGr fed the last 3 phases (YG345), 4) diets formulated with 5.0% BT fed during first 3 phases and diets containing 4.7% YGr fed during the last 2 phases (YG45), 5) diets containing 4.7% YGr fed during the first 3 phases and diets with 5.0% BT fed during the last 2 feeding phases (BT45), or 6) diets formulated with 4.7% YGr fed during the first 2 phases and diets with 5.0% BT fed during the last 3 phases (BT345). Overall performance was similar (P ≥ 0.06) among dietary treatments; however, overall ADG and ADFI increased (quadratic, P ≤ 0.05) with increasing days fed BT, but duration of dietary YGr did not affect ADG (P ≥ 0.22) or ADFI (P ≥ 0.30). There was no (P ≥ 0.23) effect of fat inclusion on carcass characteristics, but carcass lean yield decreased (linear, P = 0.02) as duration of YGr feeding increased from 37 to 103 d. Proportions of back fat SFA (quadratic, P = 0.03) and jowl fat MUFA (linear, P = 0.02) increased as the time fed BT increased from 47 to 103 d. Conversely, PUFA content of both s.c. fat depots increased (linear, P < 0.01) with increasing durations of dietary YGr. Moreover, quadratic slopes for linolenic (18:2n-6) and linolenic (18:3n-3) acids in jowl fat differed (P ≤ 0.05) between BT and YGr durations, indicating that the percentages of 18:2n-6 and 18:3n-3 increased at a greater rate with increasing time fed YGr than the rate of decreases in 18:2n-6 and 18:3n-3 associated with increasing time fed BT. Results of this study confirm that the fatty acid composition of s.c. fat depots are similar to that of the dietary fat source fed during the last 2 or 3 feeding phases, yet deposition rates of specific fatty acids appear to be dependent on the length of time pigs are fed a specific fat source.